As computers have grown increasingly important in today's society, so has the importance of computers in process control systems. Process control systems control and monitor the operation of valves, actuators, transmitters, flowmeters, and other process control and monitoring devices. Often, process control systems are used in association with other monitoring and testing systems. Such other systems often have their own displays and user interfaces which are typically separate from the process control system, and may lack the ability to communicate with the process control system.
Factories and other production plants are commonly used to create a variety of products. Process control systems, such as those provided by Fisher-Rosemount Systems, Inc., an Emerson Process Management company, are widely used in such factories and/or plants in which products are manufactured or processes are controlled (e.g., chemical manufacturing, power plant control, etc.) Process control systems are also used in the harvesting of natural resources such as, for example, oil and gas drilling and handling processes, etc. Virtually any manufacturing process, resource harvesting process, etc. can be automated through the application of one or more process control systems.
The manner in which process control systems are implemented has evolved over the years. Older generations of process control systems were typically implemented using dedicated, centralized hardware. However, modern process control systems are typically implemented using a highly distributed network of workstations, intelligent controllers, smart field devices, and the like, some or all of which may perform a portion of an overall process control strategy or scheme.
Often, process control systems are used in conjunction with external monitoring and testing equipment that is separate from the process control system as part of an overall automation system at a plant. For example, a process control system may control the operation and output of a turbine while separate vibration monitoring equipment may be used to monitor the operational health of the turbine. For another example, testing equipment, such as a valve testing device, may be periodically connected to field devices and use its own integrated display system for output. These external systems are unable to communicate with the process control system which limits access to alarms and other information generated by the external system to the external system itself and prevents access from the process control system.
One traditional technique for communicating information from the external system to the process control system has been for the control system to save the alarm changes generated by the external system in a chronologically ordered log file. For example, the Alarms and Events Custom Interface Standard from the Object Linking and Embedding (OLE) for Process Control (OPC) Foundation defines a common format for reporting alarm changes in a log file to support access to the alarms history by various applications.
Such a reporting technique has various uses and drawbacks. One important use is to allow an external system to maintain an electronic chronological log of alarm activity. One significant drawback is that the external system only sends alarm information to the log file when an alarm changes which prevents synchronization between the process control system and the external system to show the alarms that are currently active. For example, if the external system and the process control system lose communication temporarily, alarm changes may be missed and the current, correct status of the alarm may be lost. Also, important alarms are typically difficult to separate from minor alarms due to the layout of the log file and that different systems may prioritize their alarms differently. Different prioritization techniques may cause alarms from some systems to be biased as compared to other systems.